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  • Polymer and Materials Science  (94)
  • Condensed Matter: Electronic Properties, etc.  (30)
  • 1
    Electronic Resource
    Electronic Resource
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 25 (1987), S. 1967-1978 
    ISSN: 0887-624X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Dimethyl phosphonomethylheptamethylcyclotetrasiloxane (II) and 1, 3-bis(dimethyl phosphonomethyl)tetramethyldisiloxane (III) have been prepared by Arbuzov reaction of trimethyl phosphite with bromomethylheptamethylcyclotetrasiloxane (I) and 1, 3-bis(bromomethyl)tetramethyldisiloxane, respectively. Dimethyl phosphonomethylmethylsiloxane dimethylsiloxane copolymers have been prepared by acid-catalyzed ring-opening polymerization of II with hexamethyldisiloxane (MM) as an end-capping reagent and by reaction of II with III as an end-capping reagent. Dimethylsiloxane polymers with dimethyl phosphonomethyldimethylsiloxy end groups have been prepared by acid-catalyzed polymerization of octamethylcyclotetrasiloxane (D4) and III. Under these conditions hydrolysis of the dimethyl phosphonate ester groups was a problem. On the other hand Arbuzov reaction of trimethyl phosphite with bromomethylmethylsiloxane dimethylsiloxane copolymer gave a dimethyl phosphonomethylmethylsiloxane dimethylsiloxane copolymer with uniform properties. These polymers have been characterized by 1H-, 13C-, 29Si-, and 31P-NMR spectroscopy. Their molecular weight distributions have been determined by gel permeation chromatography (GPC) and their thermal stability measured by TGA.
    Additional Material: 4 Ill.
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  • 2
    ISSN: 0887-624X
    Keywords: chlorofluorocyclopropanated polymers ; carbosilane polymers ; thermal stability ; synthesis ; characterization ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Chlorofluorocarbene, generated by the sodium iodide catalyzed decomposition of phenyl(dichlorofluoromethyl)mercury, adds to the carbon-carbon double bonds of poly(1-methyl-1-phenyl-1-sila-cis-pent-3-ene) (I) and poly(1,1-dimethyl-1-sila-cis-pent-3-ene) (II) to yield poly(3,4-chlorofluoromethylene-1-methyl-1-phenyl-1-sila-cis-pent-3-ene) (CIFC-I) and poly(3,4-chlorofluoromethylene-1,1-dimethyl-1-sila-cis-pent-3-ene) (CIFC-II). Similarly, two series of random partially chlorofluorocyclopropanated polymers have been prepared. The microstructures of these adduct polymers have been determined by 1H-, 13C-, 19F-, and 29Si-NMR spectroscopy. The glass transition temperatures (Tg's) depend on the extent of chlorofluoropropanation of these polymers. These copolymers become less thermally stable as the extent of chlorofluorocyclopropanation increases. © 1993 John Wiley & Sons, Inc.
    Additional Material: 14 Ill.
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  • 3
    Electronic Resource
    Electronic Resource
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 27 (1989), S. 1499-1514 
    ISSN: 0887-624X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A precise method for the determinations of Ti+2, Ti+3 and Ti+4 was developed. The CW-procatalyst before activation contains mostly Ti+4 ions with 6% Ti+3 and 4% Ti+2 ions. Activation with AlEt3 alone at room temperature reduced all the titaniums to lower valence states consisting of 71% Ti+3 and 29% Ti+2. Reduction is incomplete when methyl-p-toluate was present as external Lewis base during activation: at 25°C the distribution of Ti+4 : Ti+3 : Ti+2 is 36% : 25% : 38%; the distribution at 50°C is 37% : 22% : 40%. Aging of the activated catalyst caused little or no changes in the distribution of [Ti+n]; whereas the catalytic activity decays rapidly with aging. The aged catalysts have polymerization activity comparable to the decreased activity of the catalyst during a polymerization. The [Ti+n] was determined for the CW-catalyst during the course of a decene polymerization; they were found to be Ti+4 : Ti+3 : Ti+2 = 30% : 27% : 43%, which did not change with polymerization time. These results suggest that the reducibility of Ti+4 species by AlEt3 or 3AlEt3/MPT to different valence states is predicated by their structures. These species do not undergo further changes in their oxidation states during either aging or polymerization. Their decays probably involve nonreductive metathesis reactions like those known for zirconium alkyls. Possible structures for the stereospecific and nonspecific sites are proposed.
    Additional Material: 4 Ill.
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  • 4
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 46 (1992), S. 167-178 
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The surface topography and pore structure of ultrafiltration membranes can be investigated with atomic force microscopy. In this study, it was found that the substitution of ethanol for water as the immersion medium improved the resolution of the fine structure of 10K polyethersulfone ultrafiltration membranes. Pores in the membrane surface from 7 to 9 nm in diameter were measured, which coincides with the range expected for 10,000 molecular weight cutoff (MWCO) ultrafiltration membranes. It is believed that this image enhancement results from increased damping and concomitant noise reduction resulting from the higher viscosity of ethanol in contrast to water.
    Additional Material: 8 Ill.
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  • 5
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 17 (1973), S. 2415-2426 
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The reaction of bisphenol A with a diglycidyl ether of bisphenol A may lead to linear polymers if a selective catalyst is used. Selective catalysts promote linear polymer formation while nonselective catalysts increase the rate of crosslinking. Selectivity in epoxy resin-bisphenol A reactions depends upon the nature of the catalyst used. In order to understand these catalyst-structure relationships better, we measured the effects of catalysts on the rate of polymerization (k1) and the rate of crosslinking (k2) during epoxy resin cures. The knowledge of the ratio k1/k2 aids in the selection of catalysts specific for the linear polymerization of epoxy resins. We related this specificity to catalysts basicity. We found that less basic catalysts tend to give large k1/k2 values, indicating that little crosslinking occurs with these highly selective catalysts. We demonstrated that the linear polymer obtained from epoxy resin polymerized by triethanolamine, a very selective catalyst, and the linear polymer prepared using 3-p-chlorophenyl-1,1-dimethylurea, a catalyst with low selectivity, are essentially the same. Finally, we caution that quantitative comparisons of selectivity should be restricted to those reactions whose kinetic reaction orders are the same.
    Additional Material: 7 Ill.
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  • 6
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 17 (1973), S. 1305-1313 
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The synergistic effect of dicyandiamide and certain trisubstituted ureas in the curing of epoxy resin is shown by differential scanning calorimetry and exotherm profiles. When 3-(p-chlorophenyl)-1,1-dimethylurea (Monuron) was reacted with dicyandiamide, we could isolate dimethylamine and a derivative of dicyandiamide. The role of these products in epoxy resin curing is speculated.
    Additional Material: 7 Ill.
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  • 7
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 29 (1984), S. 3499-3511 
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The kinetics of autoxidation of FM-73U, a rubber-modified epoxy adhesive, were investigated by Fourier transform infrared analysis. Absorbance spectra for thin samples aged in hot, moist, oxygen-rich environments were used to assess a plausible reaction mechanism; rate constants, Arrhenius plots, and oxidation rates were determined. Concurrently, crack growth rates were measured on specimens which had been exposed to similar environments for periods of up to 8 months. Paris parameters measured in these tests were correlated with the results of the oxidation studies. These correlations were used to predict the crack growth rate of the adhesive after 10 years of aging in ambient conditions. Although the prediction indicates that the adhesive becomes more brittle with age, the changes are not severe.
    Additional Material: 10 Ill.
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  • 8
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 4 (1970), S. 13-23 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Commercially available collagen membrance was evaluated as a hemodialysis membrane in the Kolff quad-coil artificial kidney. The inherent physical weakness of the membrane was strengthened by a double-screen support substracture in a coil. Greater metabolite clearance and ultrafiltration (over four times) were demonstrated with the double-screen-supported collagen coil than with either cellophane or cuprophane membrane supported by the same double-screen support substructure.
    Additional Material: 7 Ill.
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  • 9
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 9 (1975), S. 23-27 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: By means of the newly developed Replamineform process, the unique pore microstructures found in the skeletal calcium carbonate of certain reef corals can be replicated or reproduced with high precision in a wide variety of materials suitable for hard tissue implant and prosthetic applications. The advantages of fabricating porous biomaterials with this method include closely controlled size of both the pore diameters and the diameters of the pore interconnections, and virtually complete interconnection of the uniformly spaced pores. These properties are of great importance in implant devices, because tissue ingrowth, the stimulation of new bone formation, the suppression of undersirable scar tissue, the inhibition of adverse body responses, and firm biological fixation of the implanted material all depend upon the nature of the pore-microstructure configuration. Replamineform preparation of Al2O3, TiO2, hydroxyapatite, silver, Co-Cr-Mo alloys, and polymers is described in detail, and the characterization procedures used to determine the physical and structural properties of their materials are discussed. A few of the routinely measured characteristics include (1) quantitative computerized SEM image analysis for determining the volume, size and shape distributions of the macro and microporosity and the grain size measurement of the solid: (2) nondestructive x-radiography of specimens to reveal any internal defects; (3) mechanical strength measurements of randomly selected specimens. Experimental results up to now clearly demonstrate the superiority of microstructures imparted to metals, ceramics, and polymers with the Replamineform process.
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  • 10
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 9 (1975), S. 29-45 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: The Replamineform process, a new technique for the fabrication of porous hard tissue implant materials which replicates the skeletal configuration of certain marine invertebrates, was used to manufacture 1 cm long by 0.5 cm diam cylinders. The inherent advantages of porous configurations obtained through this process are controlled, uniform pore size controlled pore-microstructure ratio, and complete interconnection of pores. The specific materials studied were chrome-cobalt-molybedenum alloy, αAlO3, hydroxyapatite prepared by hydrothermal conversion, and the basic (aragonite) CaCO3 skeleton of the coral genus Porities. The implants were placed in the cancellous bone of the distal femora and proximal tibiae of adult, mongrel dogs and analyzed at 8 weeks for tissue response and ingrowth. Uniformly, new bone was found to grow into the pores of these materials and become normally mineralized. These findings were determined by microradiography, scanning electron microscopy, electron microprobe analysis, and histology. No evidences of infection, rejection, or encapsulation were seen. In the case of those CaCO3 implants left in place for 1 year, there was almost complete resorption of the cylinders, with both bony trabeculae and unmineralized collagen (presumably osteoid) found at the sites of insertion.
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